bufferevent实现的简易http client

#include "stdafx.h"
#include <event2/dns.h>
#include <event2/bufferevent.h>
#include <event2/buffer.h>
#include <event2/util.h>
#include <event2/event.h>

#include <stdio.h>

void readcb(struct bufferevent *bev, void *ptr)
{
	char buf[1024];
	int n;
	struct evbuffer *input = bufferevent_get_input(bev);
	while ((n = evbuffer_remove(input, buf, sizeof(buf))) > 0) {
		fwrite(buf, 1, n, stdout);
	}
}

void eventcb(struct bufferevent *bev, short events, void *ptr)
{
	if (events & BEV_EVENT_CONNECTED) {
		printf("Connect okay.\n");
	} else if (events & (BEV_EVENT_ERROR|BEV_EVENT_EOF)) {
		struct event_base *base = (struct event_base *)ptr;
		if (events & BEV_EVENT_ERROR) {
			int err = bufferevent_socket_get_dns_error(bev);
			if (err)
				printf("DNS error: %s\n", evutil_gai_strerror(err));
		}
		printf("Closing\n");
		bufferevent_free(bev);
		event_base_loopexit(base, NULL);
	}
}

int main(int argc, char **argv)
{
	struct event_base *base;
	struct evdns_base *dns_base;
	struct bufferevent *bev;
	
	WORD wVersionRequested;
	WSADATA wsaData;
	int err;

	wVersionRequested = MAKEWORD( 2, 2 );
	err = WSAStartup( wVersionRequested, &wsaData );
	if ( err != 0 ) {
		return -1;
	}

	if (argc != 3) {
		printf("Trivial HTTP 0.x client\n"
			"Syntax: %s [hostname] [resource]\n"
			"Example: %s www.google.com /\n",argv[0],argv[0]);
		return 1;
	}

	base = event_base_new();
	dns_base = evdns_base_new(base, 1);

	bev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE);
	bufferevent_setcb(bev, readcb, NULL, eventcb, base);
	bufferevent_enable(bev, EV_READ|EV_WRITE);
	evbuffer_add_printf(bufferevent_get_output(bev), "GET %s\r\n", argv[2]);
	bufferevent_socket_connect_hostname(
		bev, dns_base, AF_UNSPEC, argv[1], 80);
	event_base_dispatch(base);

	WSACleanup();
	return 0;
}